Fischer 344 rats and B6C3F1 mice have been exposed to arsine gas in a series of short-term inhalation studies. The collaboration of many different laboratories within the NIEHS has made it possible to investigate a variety of toxicological endpoints including histological, reproductive, hematological, immunological, and biosynthetic effects. This work will continue with an interaction study involving gallium arsenide. Subchronic exposures to methylene chloride have been conducted in preparation for a two-year chronic study. A closed exposure apparatus is being developed to measure changes in global pharmacokinetic parameters during the course of the two-year study. The ability to define the exposure environment continues to be enhanced by refinements to the facility data system. Measurements of both environmental and physiological variables are being organized in central data base where they will be accessed by standard software packages for analysis. Work is continuing on the design of a new inhalation facility. The layout of the facility has been completed. The design of the air system is in progress.